DRF的Serializer组件(源码分析)
1. 数据校验
drf中为我们提供了Serializer，他主要有两大功能：
- 对请求数据校验（底层调用Django的Form和ModelForm）
- 对数据库查询到的对象进行序列化
示例一: 基于Serializer
# models.py class UserInfo(models.Model): username = models.CharField(verbose_name='用户名', max_length=32) age = models.CharField(verbose_name='年龄', max_length=32) level_choice = ((1, 'VIP'), (2, 'SVIP'), (3, 'PARTNER')) level = models.CharField(verbose_name='级别', choices=level_choice, max_length=32) email = models.CharField(verbose_name='邮箱', max_length=32) # views.py 基于Serializer class UserSerializers(serializers.Serializer): username = serializers.CharField(label='用户名', max_length=32) age = serializers.CharField(label='年龄', max_length=32) level = serializers.ChoiceField(label='级别', choices=models.UserInfo.level_choice) email = serializers.CharField(label='用户名', min_length=6, max_length=32, validators=[EmailValidator, ]) email1 = serializers.CharField(label='用户名', min_length=6, max_length=32) email2 = serializers.CharField(label='用户名', min_length=6, max_length=32) def validate_email2(self, value): """ 钩子函数, 用于验证某个字段 """ if re.match('^w+@w+.w+$', value): return value raise exceptions.ValidationError('邮箱格式错误') class UserView(APIView): """ 用户管理 """ def post(self, request): """ 添加用户 """ ser = UserSerializers(data=request.data) # 将请求体数据传入, 这个request.data可以解析各种数据 if not ser.is_valid(): return Response({'code': 1006, 'data': ser.errors}) print(ser.validated_data) # 将数据保存到数据库 return Response({'code': 0, 'data': 'xxxx'}) 示例二: 基于ModelSerializer
# models.py from django.db import models class Role(models.Model): """ 角色表 """ title = models.CharField(verbose_name='名称', max_length=32) class Department(models.Model): """ 部门表 """ title = models.CharField(verbose_name='名称', max_length=32) class UserInfo(models.Model): username = models.CharField(verbose_name='用户名', max_length=32) age = models.CharField(verbose_name='年龄', max_length=32) level_choice = ((1, 'VIP'), (2, 'SVIP'), (3, 'PARTNER')) level = models.CharField(verbose_name='级别', choices=level_choice, max_length=32) email = models.CharField(verbose_name='邮箱', max_length=32) # 创建外键 depart = models.ForeignKey(verbose_name="部门", to="Department", on_delete=models.CASCADE) # 多对多 roles = models.ManyToManyField(verbose_name="角色", to="Role") # views.py # 基于ModelSerializer class UserModelSerializer(serializers.ModelSerializer): email1 = serializers.CharField(label='邮箱1', validators=[EmailValidator, ]) class Meta: model = models.UserInfo fields = ['username', 'age', 'email', 'email1', 'roles'] # 需要传入的数据, 多对多 extra_kwargs = { 'username': {'min_length': 4, 'max_length': 32}, 'age': {'max_length': 3} } def valicate_email(self, value): .... return value class UserView(APIView): """ 用户管理 """ def post(self, request): """ 添加用户 """ ser = UserModelSerializer(data=request.data) # 将请求体数据传入, 这个request.data可以解析各种数据 if not ser.is_valid(): return Response({'code': 1006, 'data': ser.errors}) print(ser.validated_data) # 将数据保存到数据库 ser.validated_data.pop('email1') # 删除不需要存入数据库的数据 ser.save(level=1, depart_id=1) # 加入初始化数据 return Response({'code': 0, 'data': '创建成功'}) 
2. 序列化
示例一: 序列化基本字段
class UserModelSerializer(serializers.ModelSerializer): class Meta: model = models.UserInfo fields = ['username', 'age', 'level', 'email', 'depart', 'roles'] # 序列化基本字段 class UserView(APIView): """ 用户管理 """ def get(self, request): """ 序列化数据 """ queryset = models.UserInfo.objects.all() ser = UserModelSerializer(instance=queryset, many=True) print(ser.data) return Response({'code': 0, 'data': ser.data}) 返回值:
HTTP 200 OK Allow: GET, HEAD, OPTIONS Content-Type: application/json Vary: Accept { "code": 0, "data": [ { "username": "ifeng", "age": "11", "level": 1, "email": "ifeng190410@gmail.com", "depart": 1, "roles": [] }, { "username": "Mcoco", "age": "11", "level": 1, "email": "ifeng190410@gmail.com", "depart": 1, "roles": [ 1, 2 ] } ] }
示例二: 自定义字段
from django.forms.models import model_to_dict from rest_framework import serializers from rest_framework.response import Response from rest_framework.views import APIView from api import models class UserModelSerializer(serializers.ModelSerializer): # 自定义字段 level_text = serializers.CharField(source="get_level_display") depart = serializers.CharField(source='depart.title') roles = serializers.SerializerMethodField() extra = serializers.SerializerMethodField() class Meta: model = models.UserInfo fields = ['username', 'age', 'level_text', 'email', 'depart', 'roles', 'extra'] def get_roles(self, obj): data_list = obj.roles.all() return [model_to_dict(item, ['id', 'title']) for item in data_list] def get_extra(self, obj): return 666 class UserView(APIView): """ 用户管理 """ def get(self, request): """ 序列化数据 """ queryset = models.UserInfo.objects.all() ser = UserModelSerializer(instance=queryset, many=True) print(ser.data) return Response({'code': 0, 'data': ser.data}) 返回值:
{ "code": 0, "data": [ { "username": "ifeng", "age": "11", "level_text": "SVIP", "email": "ifeng190410@gmail.com", "depart": "后端", "roles": [], "extra": 666 }, { "username": "Mcoco", "age": "11", "level_text": "VIP", "email": "ifeng190410@gmail.com", "depart": "销售", "roles": [ { "id": 1, "title": "CEO" }, { "id": 2, "title": "CFO" } ], "extra": 666 } ] }
示例三: 序列化类的嵌套
嵌套主要是面向外键和多对多表的时候
3. 数据校验&序列化
注意点:
我们在做多对多数据校验的时候, 后面如果需要新增数据, 则需要重写create方法, 如果需要更新数据, 则需要重写update方法
# mdoels.py from django.db import models # Create your models here. class Role(models.Model): """ 角色表 """ title = models.CharField(verbose_name='名称', max_length=32) class Department(models.Model): """ 部门表 """ title = models.CharField(verbose_name='名称', max_length=32) class UserInfo(models.Model): username = models.CharField(verbose_name='用户名', max_length=32) age = models.CharField(verbose_name='年龄', max_length=32) level_choice = ((1, 'VIP'), (2, 'SVIP'), (3, 'PARTNER')) level = models.SmallIntegerField(verbose_name='级别', choices=level_choice) # 类型为Int email = models.CharField(verbose_name='邮箱', max_length=32) # 创建外键 depart = models.ForeignKey(verbose_name="部门", to="Department", on_delete=models.CASCADE) # 多对多 roles = models.ManyToManyField(verbose_name="角色", to="Role") # views.py # 数据校验&序列化 class DepartModelSerializer(serializers.ModelSerializer): class Meta: model = models.Department fields = ['id', "title"] extra_kwargs = { "id": {"read_only": False}, # 数据验证, 需传入id, 为后续的create做准备 "title": {"read_only": True} # 序列化 } class RoleModelSerializer(serializers.ModelSerializer): class Meta: model = models.Role fields = ['id', "title"] extra_kwargs = { "id": {"read_only": False}, # 数据校验, 需传入id, 为后续的create做准备 "title": {"read_only": True} # 序列化 } class UserModelSerializer(serializers.ModelSerializer): level_text = serializers.CharField(source="get_level_display", read_only=True) # read_only -> 只序列化, 但是不数据校验 # Serializer嵌套，如果不设置read_only，一定要自定义create和update，自定义新增和更新的逻辑。 depart = DepartModelSerializer(many=False) roles = RoleModelSerializer(many=True) extra = serializers.SerializerMethodField(read_only=True) email2 = serializers.EmailField(write_only=True) # write_only -> 只数据校验不序列化 # 数据校验：username、email、email2、部门、角色信息 class Meta: model = models.UserInfo # username, age, email是即read_only也write_only fields = [ "username", "age", "email", "level_text", "depart", "roles", "extra", "email2" ] # 给字段添加额外参数 extra_kwargs = { "age": {"read_only": True}, "email": {"validators": [EmailValidator, ]}, } def get_extra(self, obj): return 666 def validate_username(self, value): # 钩子方法 return value # 新增加数据时, 因为无法解决m2m的储存问题. 所以需要重写create方法 def create(self, validated_data): """ 如果有嵌套的Serializer，在进行数据校验时，只有两种选择： 1. 将嵌套的序列化设置成 read_only 2. 自定义create和update方法，自定义新建和更新的逻辑 注意：用户端提交数据的格式。 """ """ validated_data: OrderedDict([('username', 'xiaoergu'), ('email', 'xiaoergu@gmail.com'), ('depart', OrderedDict([('id', 2)])), ('roles', [OrderedDict([('id', 1)]), OrderedDict([('id', 2)])]), ('email2', 'budianlong@gmail.com')]) """ depart_id = validated_data.pop('depart')['id'] # 拿到depart的id role_id_list = [ele['id'] for ele in validated_data.pop('roles')] # 拿到roles的所有id # 新增用户表 validated_data['depart_id'] = depart_id user_object = models.UserInfo.objects.create(**validated_data) # 在用户表和角色表的关联表中添加对应关系, django-orm知识 user_object.roles.add(*role_id_list) return user_object class UserView(APIView): """ 用户管理 """ def get(self, request): """ 添加用户 """ queryset = models.UserInfo.objects.all() ser = UserModelSerializer(instance=queryset, many=True) return Response({"code": 0, 'data': ser.data}) def post(self, request): """ 添加用户 """ ser = UserModelSerializer(data=request.data) if not ser.is_valid(): return Response({'code': 1006, 'data': ser.errors}) print(ser.validated_data) ser.validated_data.pop('email2') instance = ser.save(age=18, level=3) # 新增之后的一个对象（内部调用UserModelSerializer进行序列化） print(instance) # ser = UserModelSerializer(instance=instance, many=False) # ser.data return Response({'code': 0, 'data': ser.data}) 返回值:
4. 源码分析
底层源码实现：
序列化的底层源码实现有别于上述其他的组件，序列化器相关类的定义和执行都是在视图中被调用的，所以源码的分析过程可以分为：定义类、序列化、数据校验。
源码1：序列化过程
源码2：数据校验过程
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